His statement was welcomed by a wide spectrum of the public, and was the leading subject on talk-radio programmes. One caller to RTHK spoke for many when she said the current government had 'done nothing significant to guarantee the welfare of Hongkongers. But Leung clearly shows that he has a plan, even before he has taken over as chief executive.'

Critics, though, have raised concerns about what they see as Leung's high-handedness and a tendency to put himself above the rule of law. The matter will be discussed in meetings Leung will hold with other political parties in the next few days.

Lawmakers, including Liberals, said Leung's idea of setting a 'zero quota' for births by mainland mothers was a step in the right direction but that more work needed to be done to get to the root of the problem. 'It must be dealt with by addressing the issue of right of abode [for children born to mainland mothers without Hong Kong husbands] through legal means,' Lau said.

Law experts have identified four possible ways the issue can be dealt with but Huen Wong, the former president of the Law Society of Hong Kong, said each had its pitfalls and risk (see accompanying table).

'The legal experts still cannot come up with a perfect way to address the issue,' Wong said.

One of the ways under consideration is for the chief executive to approve private member's bills submitted by lawmakers to amend the Immigration Ordinance, such as those which have already been submitted by Economic Synergy lawmaker Jeffrey Lam Kin-fung and People Power lawmaker Albert Chan Wai-yip.

Lam is seeking to clarify the condition that at least one parent must be a permanent resident before babies born in Hong Kong can be granted right of abode. Chan is requesting that non-local women be obliged to declare in writing whether they are at least three months' pregnant when entering Hong Kong.

But it may be difficult for a private member's bill to pass through Legco, as nder Article 74 of the Basic Law states lawmakers may introduce only private bills that 'do not relate to public expenditure or political structure or the operation of the government', Wong said.

Even if Legco's president rules that a private member's bill can be presented and the chief executive's written consent has been obtained, the bill requires the support of a majority of both functional-constituency and directly elected lawmakers.

Wong said a better way would be to vote on a bill initiated by the government. But such a move would be risky, as amending the Immigration Ordinance would draw legal challenges and would be in conflict with a 2001 Court of Final Appeal ruling in the case of Chong Fung-yuen, which conferred the right of abode on a baby born in Hong Kong regardless of the parents' immigration status.

'The court may uphold its 2001 ruling, meaning the problem will still be unresolved,' Wong said. 'But it is also possible that the judges may come up with a new conclusion, which solves the problem once and for all. There is risk for this option as the outcome is unpredictable.'

Another option available to the government would be to wait for or initiate a case to be submitted to the Court of Final Appeal, giving the court an opportunity to override its 2001 decision - except that, as Wong pointed out, the outcome of such a lawsuit was also unpredictable.

Alan Hoo, chairman of the Basic Law Institute, supports this option, believing it is likely the court will 'rectify' its ruling on Chong Fung-yuen if the government convinces the court of its intention to formulate a law in keeping with the 1993 Sino-British Joint Liaison Group agreement. Hoo said that this stated that a child born in Hong Kong would be entitled to right of abode only if at least one parent was legally resident here at the time of its birth.

The third option for the government would be to amend Article 24 of the Basic Law, as suggested by legislator and lawyer Albert Ho Chun-yan. 'It is unprecedented in Hong Kong to amend the Basic Law, but it is perfectly legal and reasonable to change a law according to the current social circumstances. The United States has been doing this all the time. And this option could solve the problem for sure,' Ho said.

But key officials in Beijing including Wang Guangya, director of the State Council's Hong Kong and Macau Affairs Office, and Qiao Xiaoyang, director of the Basic Law Committee, are not so sure. They say that amending the Basic Law is impractical, 'will not work' and may open the door to more amendments.

The final, and perhaps most controversial move, is to seek an interpretation of the Basic Law from the Standing Committee of the National People's Congress in Beijing, either at the request of the Hong Kong government or the court, which would draw criticism the rule of law was being undermined. Beijing has indicated that it prefers to solve the issue through other channels, but has left the door open for an NPC interpretation.

Elsie Leung Oi-sie, a senior adviser to Beijing on the Basic Law, said the NPC had already given an interpretation of the Basic Law in 1999.

By the book

The four options (and their drawbacks)

Submit a private member's bill to amend Immigration Ordinance (difficult to pass through Legco)

Trigger legal procedures in Court of Final Appeal (unpredictable outcome)

Amend the Basic Law (slow and not preferred by Beijing)

Reinterpretation of Article 24 by the NPC Standing Committee (political, controversial, could lead to accusations about the rule of law being undermined)